Device for filtering a fluid especially for plastic-processing installations

ABSTRACT

The invention relates to a device for filtering a fluid, especially a liquefied plastic, said device comprising a housing, a supply channel, a discharge channel and optionally backwash channels. At least two filter elements are arranged in corresponding filter regions in the flow path of the fluid, in a filter carrier which is mounted in such a way that in can be perpendicularly displaced in relation to the direction of flow, said filter elements being able to communication with the supply channel and the discharge channel. Each filter region comprises two supply partial channels which are worked in to the filter carrier or the housing and are oriented away from the filter regions towards the discharge channel. Said discharge channel comprises housing partial channels which flow together to form the discharge channel. The supply channels can communication with the housing partial channels by displacing the filter carrier in such a way as to guide the fluid, and optionally the filter regions can be connected to the backflow channels by displacing the filter carrier.

The invention relates to a device for filtering a fluid, especially aliquefied plastic, according to the preamble of claim 1 and of claim 10.

In the following, the term “filter carrier” is used is connection withthe terms “filter” or “filter element”; it should be pointed out thatthe term “filter” or “filter element” applies to the most varied sieves,filters, and other retaining devices for contaminants.

Devices are known in the prior art, for example from DE 195 19 907 C2and EP 0 798 098 B1.

In contrast to these known devices, the invention is based on theproblem of creating an arrangement wherein the largest possible filtersurfaces are achieved simultaneously with the smallest possible filtercarrier diameters and filter changer housings. Further, the forming ofthe channels should be possible in the technically simplest manner andthe filter carrier length should be kept as short as possible.

This problem, on which the invention is based, is solved through theteaching of claim 1.

Advantageous embodiments are explained in the dependent claims.

Expressed in other words, it is proposed that the supply channel bedivided into at least two partial supply channels that, in theproduction position, lead to the actual filter regions. After thefilters are flowed through, in each filter region two filter-carrierpartial channels lead to two housing partial channels, which lead to thedischarge channel arranged opposite to the supply channel, the mergingof these at least four housing channels to the discharge channel takingplace in the wall of the housing.

In such a device, the production position, in which fluid flows throughthe two filter elements, should be realized while, simultaneously, thefilter carrier should be movable such that a replacement of the filterelements in the so-called filter change position is possible.

Through the fact that the filter-carrier partial channels leading fromthe back side of the filters to the discharge channel are formed in thefilter carrier in a substantially rectilinear manner, thus orthogonallywith respect to the longitudinal axis of the filter carrier, arelatively small cross section of the filter carrier is possible, themerging of these at least four housing partial channels to the dischargechannel taking place in the housing. Here, these channels then run tothe discharge channel obliquely with respect to the longitudinal axis ofthe filter carrier, and the production of these obliquely configuredchannels can be undertaken in the housing in a considerably easier andsimple manner than in the filter carrier itself.

Through the fact that the filter carrier has a relatively smallembodiment, the housing can be also be fashioned relatively small, whichnot only reduces the material expense, but also reduces the energyexpense for the constant heating of the arrangement as a whole.

In addition, due to the smaller frictional surface, the displacement ofthe filter carrier itself requires less force than is the case with anarrangement in which the filter carrier must have a relatively large andlong embodiment.

In a preferable embodiment form of the device according to theinvention, the supply channel and the merging of the partial housingchannels leading to the discharge channel are produced in connectionplates that can be connected to the housing, whereby again the device asa whole can be kept relatively small and the processing and productionof these different channels can be simplified.

With a device of the type according to the invention in which only asingle filter carrier is provided, in the production position acontinuous operation is possible, but in the filter change position theproduction must be interrupted. In order to avoid this, according to afurther feature of the invention it is proposed that several filtercarriers, thus at least two filter carriers, be provided, by whichmeans, when one filter carrier is displaced into the position in whichthe filters are changed, the other filter carrier ensures thatproduction still takes place.

In the devices according to the above-mentioned literature (DE 195 19907 C2 and EP 0 798 098 B1), a flow reversal of the plastic is alsopossible, this plastic being led back through the other inlet channel ofthe filter carrier in each case, and thus a backflushing of the filterarranged in this inlet channel can be effected. The backflowing plasticcan be discharged through a backflush channel. Likewise, in theabove-explained device according to the invention, it is possible torealize not only the production position, in which the two filters areflowed through by fluid, but also the backflush position of one or theother filter while simultaneously the neighboring filter maintains theproduction.

Further, an essential feature of the arrangement according to theinvention is to be seen in the fact that, through displacement of thefilter carrier, a filter region can be adjusted such that no connectionof this filter region to the supply channel and to the backflush channelexists, yet a connection of this filter region to the filter-carrierpartial channels and the housing partial channels of the other filterregion can be produced. Through this arrangement, a pressure increasefrom the back side occurs in the filter region thus blocked, so that thepressure required for the subsequently-intended backflushing of thisfilter region is prevalent in the filter region.

Finally, according to the invention it is proposed that a so-called flowdivider be arranged in the supply channel, which flow divider isprovided in front of the two filter regions and thereby forms the supplypartial channels. The flow divider effects a good flow toward the filterregions and at the same time prevents a wearing by the onflowing fluidat the dividing crosspiece in the component of the filter carrierbearing the two filters.

In addition, a flow diverter can be provided in the discharge channel,which diverter contributes to the formation of the housing partialchannels and prevents a dead space in the region of the housing partialchannels and of the discharge channel, which dead space could lead to amolecular cracking of the product possibly being deposited there.

In DE 35 27 173 C1, represented in FIG. 3 is a so-called filter changeposition, i.e. the actual filter carrier has been pulled far enough outof the housing that the filter can be removed from the filter region andreplaced by a new filter. In this so-called filter change position, thesecond filter housing in the filter carrier continues to operate, andthus makes a connection between the supply channel and the dischargechannel. During the process of pulling of the filter carrier far enoughout of the housing that the filter change position is achievable, thereis an intermediate position in which neither the filter to be replacednor the filter remaining in the filter carrier is connected to thesupply and discharge channels, so that for a more or less long period oftime the production by both filter elements is interrupted. Thisconfiguration of the filter carrier with its filters causes a brieffluctuation in the process pressure, which fluctuation isdisadvantageous for the control parameters of the subsequent units.

If the installations have a very small design, then a relatively quickdisplacement of the filter carrier can result, i.e. the fluctuation ofthe process pressure is truly quite brief. If the installations are verylarge, then a long time is necessary for the displacement of the filtercarrier, since a longer path and higher weights must be overcome, and arelatively long fluctuation in the process pressure is thereby produced,which is especially disadvantageous for the resulting unit.

The invention is further based on the problem of creating a device forfiltering a fluid, especially for plastic-processing installations, inwhich the flow of the liquefied plastic from the supply channel to thedischarge channel is fully maintained even during the displacement ofthe filter carrier for the purpose of filter changing, so that afluctuation of the process pressure is avoided.

This problem forming the basis of the invention is solved through theteaching of the independent claim 10.

Expressed in different words, it is proposed that the outlet channel ofeach filter region has an elongate form, namely elongate viewed in thedirection of the filter carrier or rather the displacement direction ofthe filter carrier, and that the discharge channel at the filter carrierend, thus directed toward the clean side of the filter, also has anelongate form viewed along the longitudinal axis of the filter carrier,but then tapers in a circular manner toward its free end, and finallythe arrangement is made such that the filter regions formed in thefilter carrier lie closely enough next to each other in the displacementdirection of the filter carrier that during the pushing out of a filterfrom the housing for the purpose of a filter change, communication isalways maintained between the supply channel and discharge channel withthe interposition of a filter, since the outlet channel of one or theother filter region always ensures a connection to the discharge channeland furthermore the supply channel to one or the other filter in thiscase always ensures a connection.

According to an essential feature of the invention, it is furtherarranged that the supply channel is divided in the housing into twopartial supply channels in each case, which lead to the filters. Here,the supply channel could also have an oval design when viewed along thelongitudinal axis of the filter carrier, but for flow-technology andmanufacturing-technology reasons it is advantageous to create partialsupply channels.

As a matter of principle, it should be pointed out that it is absolutelypossible to form both the outlet channel and the discharge channelthrough individual bores arranged in a row, and that it is likewiseabsolutely within the scope of the invention to develop the supplychannel in an add-on part that is connectable to the housing.

It is also possible in this arrangement to provide backflush channels,so that likewise in this arrangement the filter carrier or carriers canbe guided into the so-called backflush position, in which thebackflushed fluid is then released to the outside.

In the following, embodiment examples of the devices according to theinvention are explained with reference to the drawings. In the drawings:

FIG. 1 shows an embodiment form with a filter carrier inside a housingin the production position,

FIG. 2 shows the arrangement according to FIG. 1 in the so-calledblocking position,

FIG. 3 shows the arrangement according to FIG. 1 in the so-calledbackflushing position for one of the two filters,

FIG. 4 shows the arrangement according to FIG. 1 in the blockingposition for the other filter,

FIG. 5 shows the backflushing position of the arrangement according toFIG. 4,

FIG. 6 shows the position of the filter carrier according to FIG. 1 inthe so-called filter change position,

FIG. 7 shows a sectional representation of the device according to FIG.1 as viewed in the direction of the longitudinal axis of the filtercarrier,

FIG. 8 shows a sectional representation according to FIG. 7 with twofilter carriers arranged one atop the other or side by side,

FIG. 9 shows a sectional representation according to FIG. 7 with threefilter carriers arranged one atop another or side by side, wherein thehousing partial channels and the supply partial channels are provided inseparate connection plates,

FIG. 10 shows the so-called production position of a modified embodimentform,

FIG. 11 shows a selected intermediate position during the moving of thefilter carrier according to FIG. 10, said position offering abackflushing possibility,

FIG. 12 shows the filter changing of one filter in the embodiment formaccording to FIG. 10,

FIG. 13 shows the filter changing of the other filter in the embodimentform according to FIG. 10, and

FIG. 14 shows an arrangement in which two filter carriers are arrangedwith, in each case, two filters, one atop the other or side by side.

Labeled with 1 in FIG. 1 is a housing that displays a supply channel 2and a discharge channel 3. Arranged inside the housing is a filtercarrier 4 that is displaceable via means, preferably hydraulic, that arenot shown in the drawing but belong to the prior art. Arranged in amanner known per se in the filter regions 7 and 8 formed in the filtercarrier 4 are filters 5 and 6, said filters 5 and 6, as alreadyexplained, likewise being known and consisting essentially of devicesthat are capable of serving as retaining devices for contaminants.

Through the installation of a flow divider 22, the supply channel 2 isdivided into supply partial channels 24 and 25, which make possible thedelivery of the fluid to the filter regions 7 and 8.

On the downstream side of the filters 5 and 6, filter-carrier partialchannels 9 and 10 for filter region 7 and filter-carrier partialchannels 11 and 12 for filter region 8 open into the filter regions 7and 8, respectively.

In the embodiment form according to FIG. 1, these filter-carrier partialchannels 9, 10; 11, 12 lead to housing partial channels 14 and 15,respectively, for filter region 7 or to housing partial channels 16 and17, respectively, for filter region 8, which partial housing channelsare arranged in the housing.

These housing partial channels 14, 15; 16, 17 open into the dischargechannel 3, from which fluid filtered or cleansed by the filters 5, 6 canexit.

Formed in the discharge channel 3 is a flow diverter 23, which ensuresthat no dead space exists in the discharge channel 23[sic], in whichdead space filtered fluid could deposit and thus molecularly crack.

In the represented embodiment form, further provided in the housing 1 onthe side of the supply channel 2 are two backflush channels 18 and 19,which, as is still to be explained below, can be brought intocommunication with the filter regions 7, 8 on the upstream side of thefilters 5, 6 arranged in these filter regions 7, 8, whereby the devicecan be used even without the backflushing possibility.

The above explained FIG. 1 of the device shows the so-called productionposition, i.e. the fluid to be filtered is guided via the supply channel2 and the supply partial channels 24 and 25 to the upstream side of thefilters 5 and 6, is here cleansed of contaminants, via thefilter-carrier partial channels 9, 10; 11, 12 enters the housing partialchannels 14, 15; 16, 17 associated with these and formed in the housing1, and from there guided to the discharge channel 3.

If a backflushing of the filter 5 is to take place, according to FIG. 2the filter carrier 4 is displaced toward the right such that theupstream-side filter region of the filter 5 is blocked, i.e. itcommunicates with neither the supply partial channel 24 nor thebackflush channel 18. However, the downstream side of the filter 5 isconnected to the housing partial channel 14 via the filter-carrierpartial channel 10, and thus the filter region 7 is pressurized by meansof this connection.

If now, as represented in FIG. 3, through a rightward displacement ofthe filter carrier 4 a connection of the filter region 7 to thebackflush channel 18 is established, then a proper backflushing of thisfilter 5 can be carried out, while simultaneously the production can bemaintained through the feeding of the fluid via the supply channel 2 andvia the filter 6 to the discharge channel 3.

FIG. 4 shows the blocking position represented in FIG. 2 for filter 5,now for filter 6, while FIG. 5, corresponding to the representation inFIG. 3, shows the production position for filter 5 and the backflushingposition for filter 6.

In the representation according to FIG. 6, the filter carrier 4 has beendisplaced to the left far enough out of the housing 1 that now a filterchange of filters 5 and 6 can be carried out without problem.

FIG. 7 shows an arrangement of a filter carrier 4 in a housing 1,corresponding to FIGS. 1 through 6, and FIGS. 8 and 9 illustrate that itis possible to arrange several filter carriers 4 in one housing, so thata continuous production is possible when the filter associated with oneof the filter carriers 4 is replaced. Here, FIG. 9 shows that it ispossible to form the supply channel 2 and the discharge channel 3, alongwith the partial supply channels and housing partial channels associatedwith these channels 2 and 3, in connection plates 20 and 21, which canbe attached to the actual housing 1.

In the case of continuous operation with several filter carriers, theblocking of the backflush channels by suitable blocking means isnecessary in order to prevent an exiting of the material stream upon thedisplacement of the filter carrier into the filter change position.

Represented in FIG. 10 is a housing 1 in which a filter carrier 4 isdisplaceably arranged. The housing 1 displays a supply channel 2 and adischarge channel 3. A fluid, preferably a liquefied plastic, is fed tothe supply channel 2 and this fluid can contain contaminants, which areretained by filter elements, hereafter designated filters 5 and 6, thatare installed in filter regions 7, 8, so that on the clean side of thefilters cleansed fluid can be conducted, in each case via an outletchannel 29, to a discharge channel 3. Subsequent processing units, asfor example extruders, injection molding machines, granulators, or thelike, can be attached to the discharge channel 3. The discharge channel3 can here be formed in a connection plate 30.

The supply channel 2, viewed from its entrance, toward the respectivefilter regions 7, 8 splits into two supply partial channels in eachcase, 31, 32 and 33, 34 respectively. In particular, the representationin FIG. 14, in which the filter 5 is removed from a filter carrier 4,shows for the filter region 7 the fact that each filter region tapers toan oval outlet channel 29, the longitudinal axis of this oval extendingalong the longitudinal axis of the filter carrier 4 and thus having anelongate form.

FIG. 10 shows that the discharge channel 3 also has an elongate form atthe filter-carrier side when viewed along the longitudinal axis of thefilter carrier 4, but then tapers toward its open end in the manner of acircle, so that, as in the prior art, circular supply pipes for thefollowing units can be connected.

In the representation in FIG. 11 it is evident that the filter carrier 4has been displaced to the left in order to make available the filter 5for the filter change. The representation in FIG. 11 also shows that inthis intermediate position both the filter region 7 and the filterregion 8 are still connected to the supply channel 2, namely via thesupply partial channels 31, 32, and 33, while the supply partial channel34 is closed off by the actual filter carrier 4.

Also upon the further displacement of the filter carrier 4 into theposition represented in FIG. 12—thus to the left—the filter 6 withfilter region 8 always remains in communication with the supply channel2 via the supply partial channel 31, so that cleansed fluid continues tobe fed to the discharge channel 3.

FIGS. 12 and 13 show the position for the filter change of the filters 5and 6, respectively, and here too it is observable that now the supplychannel 2 is connected to the discharge channel 3 via the supply partialchannel 31 or 34, as the case may be.

Achieved through this arrangement is that temporary fluctuations in theprocess pressure do not occur, which fluctuations could affectnegatively the control parameters of the subsequent processing units.

In the case of very large installations, a large, powerful hydraulicsystem is of course required for the displacement of the filter carrierand nevertheless the displacement time for the filter carrier isrelatively long in such large installations. In this connection,achieved through the arrangement according to the invention, especiallyin the case of large installations, is the fact that a connection cannow be continuously maintained between the supply channel 2 and thedischarge channel 3 even during a relatively slow displacement of thefilter carrier 4.

In summary, it is to be stated that through the arrangement according tothe invention new filter changers are created that make available alarge filter surface, and this largest-possible filter surface orlargest-possible filter diameter is achievable in a smallest-possiblefilter-carrier diameter. Thereby, not only is the performance of thefilter device as a whole increased, but at the same time the materialcost is reduced and, simultaneously, the energy expense required tooperate this installation is reduced, i.e. the energy for thedisplacement of the filter carrier and the energy for maintaining thenecessary temperatures in the arrangement as a whole. The production ofthe downstream channels in the filter carrier is relatively simple.

Despite the fact that this arrangement has a small structural size, thecleansing of the individual filters through backflushing is possiblewithout difficulty.

Represented in FIG. 11 is a backflush possibility, namely with backflushchannels that are to be opened and closed through blocking devices.

It is to be emphasized that especially essential for the backflushing isthe fact that—before the backflushing process begins—the filter to bebackflushed can be acted upon with considerable pressure, so thatthereby the backflushing process is made substantially easier, quicker,and more effective. At the same time, small displacement movements areachieved, which is likewise significant for the energy expense.

REFERENCE NOTATION LIST

-   1 housing-   2 supply channel-   3 discharge channel-   4 filter carrier-   5 filter-   6 filter-   7 filter region-   8 filter region-   9 filter-carrier partial channel-   10 filter-carrier partial channel-   11 filter-carrier partial channel-   12 filter-carrier partial channel-   14 housing partial channel-   15 housing partial channel-   16 housing partial channel-   17 housing partial channel-   18 backflush channel-   19 backflush channel-   20 connection plate-   21 connection plate-   22 flow divider-   23 flow divider-   24 supply partial channel-   25 supply partial channel-   29 outlet channel-   30 add-on piece-   31 supply partial channel-   32 supply partial channel-   33 supply partial channel-   34 supply partial channel

1. Device for filtering a fluid, especially a liquefied plastic, saiddevice having a housing (1) with at least one supply channel (2) and adischarge channel (3), in which device at least two filter elements (5,6) are arranged in the flow path of the fluid in corresponding filterregions (7, 8) in a filter carrier (4) that is mounted such that it canbe displaced perpendicularly in relation to the flow direction, whichfilter elements can be made to communicate with the supply channel (2)and with the discharge channel (3), wherein a) each filter region (7, 8)displays two filter-carrier partial channels (9, 10; 11, 12) formed inthe filter carrier (4), which partial channels are oriented away fromthe filter region (7, 8) towards the discharge channel (3), b) thedischarge channel (3) displays four housing partial channels (14, 15;16, 17) that merge to form the discharge channel (3), c) thefilter-carrier partial channels (9, 10; 11, 12) can be made tocommunicate with the housing partial channels (14, 15; 16, 17) throughdisplacement of the filter carrier (4) in order to guide the fluid. 2.Device according to claim 1, wherein the filter carrier can be displacedsuch that both filter elements (5, 6) can be removed from their filterregions (7, 8).
 3. Device according to claim 1, wherein several filtercarriers (4) are arranged in a housing (1) one atop another or side byside.
 4. Device according to claim 1, through displacement of the filtercarrier (4) the filter regions (7, 8) can be connected to backflushchannels (18, 19).
 5. Device according to claim 4, wherein throughdisplacement of the filter carrier (4) one filter region can be adjustedsuch that no connection of the filter region exists with either thesupply channel or with the backflush channel.
 6. Device according to 4,characterized in that wherein the filter carrier (4) can be displacedsuch that one filter region produces a connection among the supplychannel (2), two filter-carrier partial channels, two housing partialchannels, and the discharge channel (3), while the other filter regionproduces a connection among a filter-carrier partial channel of the onefilter region, a housing partial channel, and a backflush channel. 7.Device according to claim 1, wherein the supply channel (2) with thesupply channels (24, 25) and the merging of the housing partial channels(14, 15; 16, 17) to form the discharge channel (3) are produced inconnection plates (20, 21) that are connectable to the housing (1). 8.Device according to claim 1, wherein a flow divider (22) is arranged inthe supply channel (2) in front of the two filter regions (7, 8). 9.Device according to claim 1, wherein a flow diverter (23) is arranged inthe discharge channel (3).
 10. Device for filtering a fluid, especiallya liquefied plastic, said device having a housing (1) with a supplychannel (2) and a discharge channel (3), in which device at least twofilter elements (5, 6) are arranged in the flow path of the fluid incorresponding filter regions (7, 8) in a filter carrier (4) that ismounted such that it can be displaced perpendicularly in relation to theflow direction, which filter elements can be made to communicate withthe supply channel (2) and with the discharge channel (3), each filterregion displaying on the clean filter side an outlet channel (9) formedin the filter carrier (4), which outlet channel is oriented away fromthe filter region (7, 8) towards the discharge channel (3), wherein a)each filter region (7, 8), viewed along the longitudinal axis of thefilter carrier (4), tapers to an outlet channel (29) having an elongateform, b) the discharge channel (3), viewed along the longitudinal axisof the filter carrier (4), has an elongate form on the filter-carrierside and tapers toward its open end in the manner of a circle, c) thefilter regions (7, 8) formed in the filter carrier (4) lie closelyenough next to each other in the displacement direction of the filtercarrier (4) that during the pushing out of a filter (5 and 6) from thehousing (1) for the purpose of a filter change, communication is alwaysmaintained between the supply channel (2) and discharge channel (3) withthe interposition of a filter (5 or 6).
 11. Device according to claim10, wherein the discharge channel (3) is formed in an add-on part (30)that is connectable to the housing (1).
 12. Device according to claim10, wherein the supply channel (2) divides in the housing (1) into twosupply partial channels in each case, (31, 32) or (33, 34) respectively,which partial channels lead to the filter elements (5, 6).
 13. Deviceaccording to claim 10, wherein the outlet channels (29) are formed asindividual bores arranged in a row.
 14. Device according to claim 10,wherein the discharge channel (3) is formed as individual recessesarranged in a row.
 15. Device according to claim 10, whereincharacterized in that the supply channel (2) is formed in an add-on partthat is connectable to the housing (1).
 16. Device according to claim10, wherein characterized in that backflush channels and blockingdevices for the latter are provided.